- #1468
- Always use `ModelExplorer` in `<select/>`, `DropDownListFor()` and `ListBoxFor()` cases
- allows evaluation of more-complex expressions
- Use `ViewData.Model` in `DropDownList()` and `ListBox()` template cases
- `ViewData` was previously ignored in these cases
nit: change `ViewDataDictionary.Eval()` to return `Model` if `expression` is `null` or empty
- now `throw` on `null` or empty `expression` name in `ViewDataEvaluator.Eval()`
- simplifies some of the higher-level code
- no change to `selectList` fallback; `Model` incorrect for that case
- no change to `GenerateRadioButton()`; would change behaviour unrelated to #1468
- this helper uses incorrect `ViewData` lookup text, see #1487
- #524
- add tests of `DropDownList` and `ListBox` HTML helpers
- extend tests of `<select/>` tag helper
- add scenario to a functional test
New `HtmlHelperSelectTest` does not cover everything. In future (see #453):
- use non-`null` `optionLabel` and `htmlAttributes` arguments
- confirm value sources and their priorities
- mock an `IHtmlGenerator` and confirm how it is called
- mock an `IHtmlHelper` and confirm how extension methods call that
Doug Bunting